The present invention relates to novel compounds, pharmaceutical compositions comprising novel compounds and novel compounds for use in medicine especially as antifungal agents. In addition, the invention provides compounds for the preparation of a medicament for use as an antifungal agent and methods of treating an individual susceptible to or suffering from an antifungal infection.
Fungal infections can affect animals including humans. These can include infections of the joints and skin. Some fungal infections occur as a result of opportunistic infection of a weakened or immune-suppressed individual. The incidence of life-threatening fungal infections has increased dramatically as the population of immunocompromised individuals (including cancer, organ transplant and AIDS patients) has increased. Present therapeutic options for the treatment of these infections are limited to two classes of compound: polyenes and azoles. The utility of polyenes is limited by nephrotoxicity and resistance is emerging to azoles. There is therefore a need for new anti-fungal compounds with novel mechanisms of action for use in treating or preventing such fungal infections.
WO94/29287 discloses arylidene-4-oxo-2-thioxo-3-thiazolidine carboxylic acids of the formula 
and their use in the treatment of atherosclerosis, arteriosclerosis and the late effects of diabetes.
WO00/18747 discloses rhodanine carboxylic acid derivatives of the formula 
for the treatment and prevention of metabolic bone disorders.
We have now found that certain thiazolidine derivatives exhibit antifungal activity.
The first aspect of the present invention provides a compound of formula I or a salt thereof 
wherein X is O or S,
A and B are OR2 or Yxe2x80x94NR3R4
wherein when A is OR2, B is Yxe2x80x94NR3R4 and vice versa,
or when one of A or B is OR2, then the other can be CO2R7,
Y is CH2 or Cxe2x95x90O,
Q is (CH2)mxe2x80x94CH(R1)xe2x80x94(CH2)n,
R is OR6 or NHR7,
R1 is hydrogen, C1-C6 branched or straight chain optionally substituted with hydroxyl, C1-C3 alkylphenyl or phenyl,
R2 is hydrogen, C1-C10 branched or straight chain alkyl or cycloalkyl, C1-C10 branched or straight chain alkenyl, C1-C10 branched or straight chain alkynyl, (CH2)mxe2x80x94(CF2)nCF3, (CH2)nxe2x80x94CH(R10)xe2x80x94(CH2)q-aryl or (CH2)p-aryl, where aryl is phenyl, pyridyl, thienyl or furyl;
wherein phenyl is optionally substituted by one or more substituents selected from F, Cl, Br, CF3, OCF3, OR6, C1-C6 branched or straight chain alkyl, COR, CN, SO2R8, SONR8R9, and pyridyl, thienyl or furyl are optionally substituted by F, Cl, Br, CF3, OR6 or C1-C6 branched or straight chain alkyl,
R3 and R4 are independently hydrogen, C1-C6 branched or straight chain alkyl, C(xe2x95x90O)R6, xe2x80x94CH(CH2OCOR8)-aryl or CH(R8)xe2x80x94(CH2)p-aryl where aryl is phenyl, pyridyl, thienyl or furyl wherein phenyl is optionally substituted by one or more substituents selected from F, Cl, Br, CF3, OCF3, OR6, C1-C6 branched or straight chain alkyl, COR, CN, SO2R8 or phenyl,
R3 and R4 may be the same or different; taken together R3, R4 may form a 4-7 membered ring optionally incorporating an additional heteroatom, for example O, N or S wherein the ring may be optionally substituted at any position with (CH2)p-aryl where aryl is phenyl optionally substituted by one or more substituents selected from F, Cl, Br, CF3, OCF3, C1-C6 branched or straight chain alkyl, COR, CN, SO2R8 or phenyl,
R5 is hydrogen, C1-C6 branched or straight chain alkyl or phenyl optionally substituted by one or more substituents selected from F, Cl, Br, CF3, OCF3, OR6, C1-C6 branched or straight chain alkyl, COR, CN or SO2R8,
R6 and R7 are independently hydrogen or C1-C10 branched or straight chain alkyl or (CH2)p-phenyl
R8 is hydrogen or C1-C3 alkyl.
R9 is C1-C6 branched or straight chain alkyl or phenyl,
R10 is hydrogen, C1-C10 branched or straight chain alkyl, (CH2)p-Aryl where aryl is phenyl optionally substituted by one or more substituents selected from F, Cl, Br, CF3, OCF3, C1-C6 branched or straight chain alkyl, COR, CN, SO2R8,
and m, n and p are integers wherein m=0xe2x88x923; n=0xe2x88x922; p=0xe2x88x923.
In a preferred embodiment compounds of formula I are provided in which:
X is O or S;
A and B are OR2 or Yxe2x80x94NR3R4
Wherein when A is OR2, B is Yxe2x80x94NR3R4 and vice versa,
or when one of A or B is OR2, then the other can be CO2R6;
Y is CH2 or Cxe2x95x90O;
Q is CH(R1);
R is OH;
R1 is hydrogen, C1-C6 alkyl or C1-C3 alkylphenyl;
R2 is hydrogen, C1-C10 branched or straight chain alkyl, (CH2)p-phenyl, wherein phenyl is optionally substituted by one or more substituents selected from F and CF3;
R3 and R4 are independently hydrogen, C1-C6 branched or straight chain alkyl, (CH2)p-phenyl, C(xe2x95x90O)C1-C10 branched or straight chain alkyl, xe2x80x94CH(CR8)-phenyl xe2x80x94CH(CH2OCOR8)-phenyl, or R3 and R4 together form a morpholino, piperidinyl or piperazinyl group optionally substituted with (CH2)p-phenyl; and
R5 is hydrogen; and wherein p is an integer=0-3.
Preferred compounds of the invention include;
5-[[[3-(N-methyl-N-phenylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N,N-Dibenzylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N,N-Dipentylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-((S)-N-Benzyl-N-alpha-methylbenzylamino)carbonyl-4-(phenyl-methoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N,N-Dibutylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N-Benzyl-N-butylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-((R)-N-alpha-methylbenzylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-((S)-N-methyl-N-alpha-methylbenzylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(Dipentylamino)carbonyl-4-methoxy]phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-((S)-N-Benzyl-N-alpha-methylbenzylamino)carbonyl-4-methoxy]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N,N-Dipentylamino)carbonyl-4-[(2,4-difluorophenyl)-methoxy]]phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N,N-Dipentylamino)carbonyl-4-(trifluorophenyl)-methoxy]phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[3-[(Dibenzylamino)methyl]-4-(phenylmethoxy)phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[3-[(Dipentylamino)methyl]-4-(phenylmethoxy)phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
(R)-5-[[[3-(N-xcex1-(Acetoxymethyl)benzyl-N-benzylamino)carbonyl-4-(phenylmethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[[3-(N,N-Dipentylamino)carbonyl-4-(2-phenylethoxy)]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid;
5-[[4-(2-Phenylethoxy)-3-[(N-phenyl-N-2-n-propyl-n-pentylcarbonyl)aminomethyl]-phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid.
The invention also extends to prodrugs of the aforementioned compounds. A prodrug is commonly described as an inactive or protected derivative of an active ingredient or a drug which is converted to the active ingredient or drug in the body. In addition, the invention extends to active derivatives of the aforementioned compounds.
Where a compound of the invention contains one or more chiral centres, the compound can be provided as a single isomer (R or S) or a mixture of isomers for example, a racemic mixture. Where a substituent contains an alkene moiety, the alkene can be present as a cis or trans isomer or a mixture thereof.
Examples of pharmaceutically acceptable salts of the above compounds include those derived from inorganic and organic bases. Examples of suitable inorganic bases for the formation of salts of compounds for this invention include the hydroxides, carbonates, and bicarbonates of ammonia, lithium, sodium, calcium, potassium, aluminium, iron, magnesium, zinc and the like. Salts can also be formed with suitable organic bases. Such bases suitable for the formation of pharmaceutically acceptable base addition salts with compounds of the present invention include organic bases that are nontoxic and strong enough to form salts. Such organic bases are already well known in the art and may include amino acids such as arginine and lysine, mono-, di-, or trihydroxyalkylamines such as mono-, di-, and triethanolamine, choline, mono-, di-, and trialkylamines, such as methylamine, dimethylamine, and trimethylamine, guanidine; N-methylglucosamine; N-methylpiperazine; morpholine; ethylenediamine; N-benzylphenethylamine; tris(hydroxymethyl)aminomethane; and the like. Where appropriate salts can also be formed with organic acids such as methanesulphonic acid, benzenesulphonic acid and p-toluenesulphonic acid, or mineral acids such as hydrochloric and sulphuric acid and the like, giving methanesulphonate, benzenesulphonate, p-toluenesulphonate, hydrochloride and sulphate salts, and the like, respectively.
Salts may be prepared in a conventional manner using methods well known in the art.
The second aspect of the invention relates to a pharmaceutical composition of a compound of the first aspect of the invention. The pharmaceutical formulation will provide a compound of the first aspect of the invention and, optionally, a pharmaceutically acceptable carrier.
The pharmaceutical composition may be adapted for administration by any appropriate route, for example by the oral (including buccal or sublingual), rectal, nasal, topical (including buccal, sublingual or transdermal), vaginal or parenteral (including subcutaneous, intramuscular, intravenous or intradermal) route. Such compositions may be prepared by any method known in the art of pharmacy, for example by admixing the active ingredient with the carrier(s) or excipient(s) under sterile conditions.
Pharmaceutical compositions adapted for oral administration may be presented as discrete units such as capsules or tablets; as powders or granules; as solutions, syrups or suspensions (in aqueous or non-aqueous liquids; or as edible foams or whips; or as emulsions).
Suitable excipients for tablets or hard gelatine capsules include lactose, maize starch or derivatives thereof, stearic acid or salts thereof.
Suitable excipients for use with soft gelatine capsules include for example vegetable oils, waxes, fats, semi-solid, or liquid polyols etc.
For the preparation of solutions and syrups, excipients which may be used include for example water, polyols and sugars. For the preparation of suspensions, oils (e.g. vegetable oils) may be used to provide oil-in-water or water in oil suspensions.
Pharmaceutical compositions adapted for transdermal administration may be presented as discrete patches intended to remain in intimate contact with the epidermis of the recipient for a prolonged period of time. For example, the active ingredient may be delivered from the patch by iontophoresis as generally described in Pharmaceutical Research, 3 (6):318 (1986).
Pharmaceutical compositions adapted for topical administration may be formulated as ointments, creams, suspensions, lotions, powders, solutions, pastes, gels, sprays, aerosols or oils. For infections of the eye or other external tissues, for example mouth and skin, the compositions are preferably applied as a topical ointment or cream. When formulated in an ointment, the active ingredient may be employed with either a paraffinic or a water-miscible ointment base. Alternatively, the active ingredient may be formulated in a cream with an oil-in-water cream base or a water-in-oil base. Pharmaceutical compositions adapted for topical administration to the eye include eye drops wherein the active ingredient is dissolved or suspended in a suitable carrier, especially an aqueous solvent. Pharmaceutical compositions adapted for topical administration in the mouth include lozenges, pastilles and mouth washes.
Pharmaceutical compositions adapted for rectal administration may be presented as suppositories or enemas.
Pharmaceutical compositions adapted for nasal administration wherein the carrier is a solid include a coarse powder having a particle size for example in the range 20 to 500 microns which is administered in the manner in which snuff is taken, i.e. by rapid inhalation through the nasal passage from a container of the powder held close up to the nose. Suitable compositions wherein the carrier is a liquid, for administration as a nasal spray or as nasal drops, include aqueous or oil solutions of the active ingredient.
Pharmaceutical compositions adapted for administration by inhalation include fine particle dusts or mists which may be generated by means of various types of metered dose pressurised aerosols, nebulisers or insufflators.
Pharmaceutical compositions-adapted for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations.
Pharmaceutical compositions adapted for parenteral administration include aqueous and non-aqueous sterile injection solution which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation substantially isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. Excipients which may be used for injectable solutions include water, alcohols, polyols, glycerine and vegetable oils, for example. The compositions may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carried, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets.
The pharmaceutical compositions may contain preserving agents, solubilising agents, stabilising agents, wetting agents, emulsifiers, sweeteners, colourants, odourants, salts (substances of the present invention may themselves be provided in the form of a pharmaceutically acceptable salt), buffers, coating agents or antioxidants. They may also contain therapeutically active agents in addition to the substance of the present invention.
Dosages of the substance of the present invention can vary between wide limits, depending upon the disease or disorder to be treated, the age and condition of the individual to be treated, etc. and a physician will ultimately determine appropriate dosages to be used. This dosage may be repeated as often as appropriate. If side effects develop the amount and/or frequency of the dosage can be reduced, in accordance with normal clinical practice. The likely dosage of the substance is an effective dosage of 0.1-750 milligrams/kg/day, preferably 0.1-10 milligrams/kg/day.
It should be understood that in addition to the ingredients particularly mentioned above, the formulations may also include other agents conventional in the art having regard to the type of formulation in question, for example those suitable for oral administration may contain flavouring agents.
All preferred features of the first aspect of the invention also apply to the second aspect.
A third aspect of the invention provides a method for the manufacture of the compounds of the first aspect of the invention.
The compounds of this invention can be prepared by condensation of rhodanine-3-acetic acid or an analogue or derivative thereof with the appropriate substituted benzaldehyde derivative under general acid-base catalysis conditions using typical reagents for such a process, e.g. sodium acetate in acetic acid or ammonium acetate in a suitable solvent such as toluene, usually with the application of heat and preferably at the reflux temperature of the solvent (Scheme 1). 
Rhodanine-3-acetic acid and the benzaldehyde derivatives are either commercially available, can readily be prepared by a skilled person or are synthesised by the methods outlined in the examples.
A compound of general formula (I) may be transformed into another compound of general formula (I) using methods well known to those skilled in the art. If protection of a particular functional group is required, this can be achieved using protecting groups and conditions known in the art. The protecting groups may be removed at any stage in the synthesis of the compounds of formula I or may be present on the final compound of formula I.
The third aspect of the invention also provides novel intermediate compounds in the formation of compounds of formula I.
All preferred features of the first and second aspects of the invention also apply to the third aspect.
The fourth aspect of the invention provides a compound of the first aspect of the invention for use in medicine.
In one feature of the fourth aspect of the invention provides a compound of formula I for use as an anti-fungal agent.
For the purposes of this invention, an anti-fungal agent is a compound or composition which alleviates or reduces the symptoms of a fungal infection or an agent which causes harm to fungus allowing the destruction of a fungus either by the agent, a second agent or the hosts natural defenses (e.g. the immune system). The anti-fungal agent can be used in the curative or prophylactic treatment of fungal infections.
The fourth aspect provides a compound which can be administered to humans or animals especially domestic animals such as dogs, cats, horses etc.
The compound of the first aspect of the invention can be used to treat topical infections caused by species of fungus including Candida, Trichophyton, Microsporum and Epidermophyton or in mucosal infections caused by species of fungus including Candida albicans (e.g. thrush and vaginal candidiasis). They can also be used in the treatment of infections caused by, for example, species of Candida (e.g. Candida albicans), Cryptococcus neoformans, Aspergillus flavus, Aspergillus fumigatus, Coccidioides, Paracoccidioides, Histoplasma or Blastomyces.
The cell wall of Candida and other pathogenic fungal species is essential for the survival of the organism. Defects in the wall structure will result in cell swelling and ultimately death through rupture. The unique nature of the wall has made its synthesis and re-modelling a focus for the development of novel anti-fungal agents. The wall consists of three major components: complex xcex21-3 and xcex21-6 linked glucan chains, chitin and cell wall mannoproteins. The xcex2-glucans represent 50-60% of the cell wall mass, forming a rigid skeletal structure responsible for shape and physical strength. The chitin is only a minor component ( greater than 3%), but forms a structure to which the xcex2-glucan is linked and is essential for bud scar formation during cell division. There are a number of agents that are being developed as anti-fungal treatments targeted against xcex2-glucan (lipopeptides, e.g. echinocandins and pneumocandins (Kurtz, M. B. and Douglas, C. M. (1997) J. Med. Vet. Myc. 35, 79-86.)) and chitin (e.g. nikkomycin Z (Obi, K. Uda, J. Iwase, K. Sugimoto, O. Ebisu, H. and Matsuda, A. (2000) Bioorg. Med. Chem. Lett. 10, 1451-4)) synthesis.
The mannoproteins represent the remaining content of the wall. They form radially extending fibrillae at the outside of the cell wall and are believed to confer the cell surface properties involved in adhesion and host interactions. A number of classes of mannoproteins have been identified (e.g. Sed1, Flo11, Aga1, Pir2, Als1, Ax12) and these have been separated into groups dependent upon the nature of their attachment to the other cell wall components (Kapteyn, J. C. Hoyer, L. L. Hecht, J. E. Muller, W. H. Andel, A. Verkleij, A. J. Makarow, M. Van Den Ende, H. and Klis, F. M. (2000) Mol. Microbiol. 35, 601-11). During their secretion from the cell some receive a GPI anchor and all become mannosylated. Mannosylation of these proteins is divided into two categories: O- and N-linked. The N-linked are attached via asparagine residues and form extensive branched structures consisting of an xcex11,6 backbone to which xcex11,2-, xcex11,3- and xcex21,2-side chains are attached. The O-linked are attached via serine or threonine residues and consist of short linear chains. The extension of both chain types is catalysed by a family of mannosyltransferases. The initial mannose residue is added to serine or threonine by a protein:mannosyl transferase (PMT) which uses dolicholphospho-mannose as a donor of the mannose. Seven PMT""s have been reported in S. cerevisiae (Strahl-Bolsinger, S. Gentzsch, M. and Tanner, W. (1999) Biochim. Biophys. Acta. 1426, 297-307) and by homology five have been identified to date in Candida (homologues have also been found in Aspergillus and other fungal species). It appears that members of the family show some substrate specificity (Sanders, S. L. Gentzsch, M. Tanner, W. and Herskowitz, I. (1999) J. Cell. Biol. 145, 1177-88) but this has not been clearly defined.
Although a human homologue has been found and evidence of O-mannosylation in some tissues, no activity has been recorded in mammalian tissue.
Deletion of both copies of the PMT1 gene from Candida albicans results in a strain that is no longer virulent in animal models (Timpel, C. Strahl-Bolsinger, S. Ziegelbauer, K. and Ernst, J. F. (1998) J. Biol. Chem. 273, 20837-46). The strain also shows a failure to form pseudohyphae under conditions of nitrogen starvation and increased sensitivity to agents associated with cell wall defects.
Without being bound by scientific theory it is proposed that the compounds of the invention inhibit the protein mannosyl transferase enzyme, preventing the formation of the O-linked mannoproteins and compromising the integrity of the fungal cell wall. Defects in the wall structure have been shown to result in cell swelling and ultimately death through rupture.
All preferred features of the first, second and third aspects of the invention also apply to the fourth aspect.
A fifth aspect of the invention provides the use of a compound of formula I or a salt thereof in the manufacture of a medicament for use as an antifungal agent.
For the purposes of this invention, the medicament can be used in the curative or prophylatic treatment of fungal infections in humans and animals.
The medicament comprising one or more compound of formula I will usually be supplied as part of a sterile, pharmaceutical composition which will normally include a pharmaceutically acceptable carrier. This pharmaceutical composition may be in any suitable form as described in the second aspect of the invention, depending on the desired method of administering it to a patient.
It may be provided in unit dosage form, will generally be provided in a sealed container and may be provided as part of a kit. Such a kit would normally (although not necessarily) include instructions for use. It may include a plurality of said unit dosage forms.
All preferred aspects of the first, second, third and fourth aspects of the invention also apply to the fifth aspect.
A sixth aspect of the invention provides a method of treatment for treating an individual suffering from a fungal infection comprising administering to the individual a compound of the first aspect of the invention. The treatment may be prophylactic or in respect of an existing condition.
The compound of the first aspect can be administered as a pharmaceutical composition in combination with a pharmaceutically acceptible excipient as described in the second aspect of the invention. The pharmaceutical composition can comprise one or more of the compounds of the first aspect.
The method of treatment will provide the compound of the first aspect at an effective dosage of 0.1-750 milligrams/kg/day, preferably 0.1-10 milligrams/kg/day. The compounds can be administered once or more a day, twice a week, weekly, every two weeks or monthly.
The compound or pharmaceutical composition can be administered simultaneously, separately or sequentially with another anti-fungal treatment.
A particular feature of the fifth and sixth aspects is the treatment of individuals who are immunosuppressed as a result of a therapy (e.g. chemotherapy or radiotherapy), organ transplant or an infection (e.g. HIV).
The method can be used to treat topical infections caused by species of fungus including Candida, Trichophyton, Microsporum and Epidermophyton or in mucosal infections caused by species of fungus including Candida albicans (e.g. thrush and vaginal candidiasis). The method can also be used in the treatment of infections caused by, for example, species of Candida (e.g. Candida albicans), Cryptococcus neoformans, Aspergillus flavus, Aspergillus fumigatus, Coccidioides, Paracoccidioides, Histoplasma or Blastomyces.
All preferred features of the first, second, third, fourth and fifth aspects of the invention also apply to the sixth aspect.
The invention will now be illustrated by reference to one or more of the following non-limiting examples.